The present invention relates to fuel caps for closing filler necks of vehicle fuel tanks. More particularly, the present invention relates to a threaded fuel cap that enables fuel vapor to vent from the tank upon rotation of the fuel cap in the removal direction.
Conventional fuel caps for closing the filler neck of vehicle fuel tanks generally include a pressure-vacuum valve located in the cap to control the pressure within the fuel tank. Whenever the pressure within the tank reaches a predetermined superatmospheric level, the pressure valve portion of the pressure-vacuum valve automatically opens to prevent excess pressure build up. Whenever the pressure within the tank drops to a predetermined subatmospheric level, the vacuum valve portion of the pressure-vacuum valve opens to equalize the pressure in the tank.
The pressure-vacuum valve in a conventional fuel cap must be adjusted so that the potential for some vapor pressure to remain in the fuel tank exists at all times. Generally, the pressure maintained within the fuel tank is in the range of 1-2 psi. This retention of some level of fuel vapor in the tank is desired for several reasons, and normally does not create any problems. However, under certain conditions, pressure from fuel vapor can result in fuel and fuel vapor escaping from the filler neck once the fuel cap is removed. This rapid escape, or surge, of the fuel and fuel vapor from the filler neck after cap removal can result in emission of a potentially dangerous fuel vapor concentration level in the region surrounding the filler neck, as well as the possibility that the person removing the cap could be injured by hot fuel spray.
With larger fuel tanks now being utilized in many vehicles, and, particularly, with the use of newer, more volatile blends of fuel having higher than normal Reid vapor pressure, more than normal fuel vapor pressure may be generated in these fuel tanks, particularly in warm or hot weather or after the vehicle has been running. Therefore, it would be advantageous to provide a fuel cap that will enable fuel vapor to be vented from the fuel tank sometime during the cap removal operation, but before the cap is actually removed from the filler neck. Ideally, when the cap is used in the manner described hereinafter, this venting will be a controlled, metered venting of the fuel vapor with the fuel vapor being directed away from the operator.
Threaded caps that engage threads in the filler neck of vehicles are now widely used because of their ease of installation and removal, and because of their excellent sealing characteristics. Therefore, it would be advantageous to provide a fuel cap that will enable the fuel tank to be vented in a controlled manner upon rotation of the cap in the cap removal direction to allow the fuel vapor to be vented before the cap is removed
Most conventional threaded fuel caps include a primary seal that is adapted to engage a sealing lip on the filler neck when the cap is rotated fully in the cap installation direction. These conventional threaded fuel caps generally have an outer cover that is configured to be gripped by the operator to rotate the cap. Because unseating of the primary seal can result in a surge of fuel and fuel vapor from the filler neck in warm or hot weather, or after the vehicle has been running, it would also be advantageous to provide a fuel cap that enables fuel vapor to be vented from the tank in a controlled manner upon rotation of the outer cover before the seal between the primary seal and the filler neck is broken.
It is therefore one object of the present invention to provide a fuel cap that will enable fuel vapor to be vented from the fuel tank before the fuel cap is removed from the filler neck.
Another object of the present invention is to provide a fuel cap that will enable fuel vapor to be vented from the tank automatically during a portion of the cap removal procedure.
Yet another object of the present invention is to provide a fuel cap that will enable fuel vapor to be vented from the tank in a controlled manner while maintaining the primary seal between the fuel cap and the filler neck.
Still another object of the present invention is to provide a fuel cap having a controlled release fuel vapor venting system that enables fuel vapor to be dissipated during cap removal so as to reduce the concentration of fuel vapor in the local region surrounding the filler neck, as well as reduce the risk of expulsion of fuel from the filler neck.
According to the present invention, a fuel cap is provided for use in a threaded filler neck of a fuel system. The fuel cap includes shell means for providing a hand grip and closure means for rotatably engaging the threaded filler neck for closing the filler neck. The closure means includes seal means for establishing a seal with the filler neck to block the escape of fuel and fuel vapor in the filler neck to the atmosphere. The cap also includes pressure-relief means extending through the closure means for venting pressurized fuel vapor in the filler neck through the closure means. The cap further includes actuation means for providing an operative connection between the shell means and the pressure-relief means so that rotation of the shell means relative to the filler neck in a cap-removal direction will actuate the pressure-relief means without substantially rotating the closure means relative to the filler neck and breaking the seal established by the seal means.
One feature of the present invention is that the actuation means provides an operative connection between the shell means and the pressure-relief means so that rotation of the shell means relative to the filler neck in a cap-removal direction will actuate the pressure-relief means. One advantage of this feature is that rotation of the shell means in a cap-removal direction automatically actuates the pressure-relief means to enable the fuel vapor to be vented from the tank.
Another feature of the present invention is that the fuel cap produces an audible hissing sound as fuel vapor escapes through the closure means upon actuation of the pressure-relief means. Advantageously, this hissing sound provides an indication to the operator that fuel vapor is being vented and that continued rotation of the shell means in the cap removal direction should be delayed until the sound has ceased.
Another feature of the present invention is that the shell means and the actuation means cooperate to actuate the pressure-relief means without substantially rotating the closure means relative to the filler neck and breaking the seal established by the seal means. One advantage of this feature is that the seal established by the seal means between the closure means and the filler neck is maintained until the fuel vapor is vented from the tank. This permits venting of the fuel vapor from the tank in a controlled manner.
In preferred embodiments of the present invention, the shell means and the closure means cooperate to define outlet-deflector means for discharging fuel vapor vented through the closure means via the pressure-relief means from the cap to a region outside of the filler neck in a direction toward the filler neck and generally away from a person manually rotating the shell means.
One feature of the foregoing structure is that outlet-deflector means are provided for directing the flow of fuel vapor from the cap. One advantage of this feature is that the vented fuel vapor is directed toward the filler neck and away from the person manually rotating the shell means.
Also in preferred embodiments of the present invention, the actuation means includes a drive hub that is coupled to the shell means, a plunger that is axially movable in the closure means between an inactive position and a vacuum-relief valve-actuating position, and first camming means interconnecting the drive hub and the plunger for urging the plunger in an axial direction toward its vacuum-relief valve-actuating position in response to rotation of the drive hub in the cap-removal direction.
One feature of the foregoing structure is that rotation of the shell means in the cap-removal direction rotates the drive hub which interconnects with the plunger through camming means to urge the plunger in a direction to actuate the vacuum-relief valve. One advantage of this feature is that the vacuum-relief valve is automatically actuated upon rotation of the shell means in the cap-removal direction.
Advantageously, the camming means can be configured to control sequentially the actuation of the vacuum-relief valve and the disengagement of the closure means from the filler neck as a function of the angular movement of shell means relative to the filler neck. Crashworthiness of the fuel cap is improved by imposing a slight delay in valve actuation. Furthermore, following the slight delay, the pressurized fuel vapor is released to the atmosphere over a maximized period of time, due, in part, to the subsequent quick opening of the valve by the plunger followed by a "lost motion" time delay prior to establishing a driving connection between the shell means and the closure means. This extra time allows the fuel vapor to be released, diffused, or dissipated in a direction toward the vehicle itself without reaching high fuel vapor concentrations in the vicinity occupied by the user during cap removal.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.